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Oblique Rotating Ion Implantation Simulation for the Drain Formation of Gate/N- Overlapped LDD MOSFET's Using the Monte Carlo Method
IEICE TRANSACTIONS on Electronics
Publication Date: 1991/06/25
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Device and Process Simulation for Ultra Large Scale Integration)
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A three-dimensional simulation program of oblique rotating ion implantation using the Monte Carlo method has been newly developed to simulate the N- and N+ drain formation of the gate/N- overlapped LDD MOSFET's. The binary scattering approximation is used for nuclear scattering, and the Lindhard-Scharff formula and the Bethe-Bloch formula are used for electronic scattering. The azimuth of the ion is initialized by a random number uniformly distributed between 0 and 2π to express the wafer rotation. The topography of the MOSFET's is approximately expressed in algebraic form to obtain effectively the touchdown points of ion particles on the target surface. The vectorized Monte Carlo method is used to reduce the CPU time. The simulation provides the two-dimensional distribution of the dopant and the Frenkel pairs (vacancy-interstitial), using the Kinchin-Pease equation. From the results of the calculation, it appears that the overlap length, which is defined as the distance between the polysilicon gate edge and the intersection of the 104/cm (equi-concentration/doseline) on the silicon surface, increases in accordance with the increase of the incidence angle of the ion beam, and it extends to 0.1 µm when 40-keV of phosphorus is implanted with an incidence angle of 60. It also appears that the concentration of the Frenkel pairs becomes lower in accordance with an increase in the incidence angle of the ion beam. The simulation also reveals that the effect of a shadowed drain region caused by the polysilicon gate is enlarged in accordance with the increase in the incidence angle, especially in the case of an incidence angle of 60, when the shadowed N+ drain region extends to the point 0.6 µm from the edge of the sidewall which is 0.35 µm in height.